Blast victim had planned to leave the Navy to get married

A sailor killed in an explosion aboard a British nuclear submarine planned to leave the Royal Navy within weeks to marry his American fiancée, it has emerged.

Tributes were paid to 32-year-old Leading Operator Mechanic Paul McCann and his young crewmate Anthony Huntrod, aged 20.

Both weer killed in the incident aboard the hunter-killer submarine HMS Tireless on Wednesday morning as the warship took part in a wargame exercise beneath the Arctic ice cap.

Paul McCann (left) and Anthony Huntrod died on board HMS Tireless

Investigators are still trying to establish why a back-up oxygen generator exploded without warning, killing one sailor instantly and leaving the other dead from smoke inhalation within minutes.

A third crew member who suffered from smoke inhalation and was airlifted to safety after the submarine surfaced through the icepack, was recovering well in a U.S. military hospital, officials said.

Despite the deaths, HMS Tireless resumed her role in the exercise and was last night back beneath the polar ice simulating a battle against the American submarine USS Alexandria.

A Board of Inquiry will begin when Tireless returns to her home port of Plymouth.

It will focus on the submarine's Self-Contained Oxygen Generator, a back-up air processor which burns special chemical 'candles' at high temperature to give off oxygen when the submarine's main air systems are out of action and which apparently exploded.

Two sailors have been killed onboard the nuclear submarine HMS Tireless

Commanders locked in a tense, silent hunt for another submarine sometimes order the main systems to be shut down for hours at a time to make their vessel even quieter and minimise the chances of being detected, and then burn the special candles to keep oxygen levels on board within safe limits.

The chlorate candles smoulder at around 600 degrees centigrade inside a special insulated container, and investigators will try to establish whether the device failed in some way, causing the explosion and fire.

HMS Tireless was launched in 1984, and has been at sea taking part in the training exercise for three weeks.

The oxygen generator was installed as part of a refit six years ago, and according to the MOD it has had a 100 per cent safety record until now. Leading Operator Mechanic Paul McCann came from Halesowen in the West Midlands.

He had served aboard HMS Tireless for three years but had recently applied to leave the Navy and was planning to marry his American fiancée Julie, and move to Philadelphia.

The Navy described him as a "talented, charismatic and cheerful man" whose leadership skills had won him rapid promotion, and who thrived on looking after the junior crewmates. Commander of HMS Tireless Iain Breckenridge RN said: "He was simply the kind of man a Commanding Officer could call on at any time and in any circumstances - his exuberance, good humour and huge personality is greatly missed by all of his shipmates." His mother Pauline, Father Brian and sister Sharon issued a statement paying tribute to "a caring and gentle man who loved his family." Operator Maintainer Anthony Huntrod, from Sunderland, had served aboard HMS Tireless for just nine months after passing stringent selection procedures to become a submariner.

Commander Breckenridge said: "I consider myself fortunate and privileged to have worked with such a committed, capable and effervescent young man and it was rare that I talked to him without both of us breaking into beaming smiles.

"Anthony stood at the cusp of a successful career. His loss has been profoundly felt by all onboard."

His parents issued a statement saying: "Anthony was our son. He will be greatly missed by us for the rest of our lives.

"He was over the moon when he joined the Navy two years ago. He greatly loved the Navy and the job that he did."

All Royal Navy submarines have been ordered to stop using the oxygen candle equipment until the latest incident has been fully investigated.

The deaths are thought to be the first in the British submarine fleet since 1997, when a sailor was killed in a fall from HMS Spartan while she was surfaced in the Irish Sea.